To establish the effect of long-term treatment with raloxifene, compared with placebo, on the rate of new vertebral fractures in osteoporotic postmenopausal women with and without prevalent vertebral fractures. To establish the safety of chronic administration of raloxifene in postmenopausal women with osteoporosis. To establish the effect of long-term treatment with raloxifene, compared with placebo, on lumbar spine and femoral neck bone mineral density (BMD) in postmenopausal women with osteoporosis.